Many hydroponic systems involve the recovery and re-use of an aqueous nutrient. Aeroponic systems, in which plant roots are suspended in air in an enclosure and nutrient is sprayed onto the roots in the form of a mist or fine drops, make up one sub-category of such systems. Another sub-category is “Ebb and Flow” systems, in which plants are placed in a medium such as expanded clay pellets in a growing tray at the top of a growing chamber, connected to a nutrient reservoir. The aerated nutrient is alternately pumped to flood the roots in the growing tray, and allowed to drain back into the reservoir thereby exposing the roots to fresh air drawn from outside.
Ebb and flow systems require a relatively large volume of nutrient, to ensure that the medium holding the plant roots can be adequately flooded. Another disadvantage of ebb and flow systems is inadequate aeration. In particular, the plant roots may grow sufficiently dense to cause nutrient trapping and air depletion, which may lead to diseases such as root rot.
Aeroponic systems have been developed to address the issues of inadequate aeration and high nutrient volume by keeping the plant roots suspended in air, and delivering nutrient directly to the roots in the form of a nutrient spray. They generally use submersible pumps to pump the nutrient from a pool at the base of the growing chamber to nozzles positioned closer to the roots and directed towards the roots. However, as the roots grow down, the roots may get submerged in the pool of nutrient, where oxygen content is intrinsically low. Hence it is generally necessary to provide aeration within the pool, and support from external aeration systems like air pumps or bubblers may be required. An alternate configuration in aeroponic systems is to grow the roots entirely in nutrient mist, using a high pressure pump in an external reservoir to feed the nozzles with the nutrient. After spraying, residual nutrient is returned to the external reservoir. These systems are relatively complex, and more suitable for large gardens where a great many plants are to be supported.
Another problem with current aeroponic systems is that their performance is seriously affected by any blockages occurring in the spray nozzles. Detecting and correcting such blockages is a time consuming and inconvenient manual process, especially in large gardens.
There is therefore a need for a simple and reliable aeroponic system that is scalable for small and large gardens, requires relatively low volumes of nutrient and water, and provides improved aeration and expulsion of stale air without the use of external aeration systems or reservoirs. Ideally, such a system would also be flexible (for example, allowing convenient adjustment of the nutrient as and when necessary), and be reliable in operation, with improved tolerance to nozzle blockage.